The invention relates generally to multi-conductor routing schemes, and more particularly an interface module for a high-performance semiconductor tester interface.
Sophisticated electronic assemblies often employ dense arrays of electrical conductors to deliver signals from one area to another. Routing large groups of conductors in an efficient and organized manner often proves problematic for a variety of reasons. The overall assembly cost, formfactor (size), conductor pitch and complexity all must typically be taken into account to determine a suitable routing method.
For high-performance semiconductor testers, tester signals up to several gigahertz are funneled and delivered from relatively large circuit boards known as channel cards, to the leads of a very compact device-under-test. Often, several thousand signal paths provide the signal delivery scheme between the DUT and the tester electronics. In order to preserve fidelity for such high-frequency signals, the signal paths are constructed to provide as close to a matched fifty-ohm impedance environment as possible. Providing such an environment with a large number of signal paths is a difficult endeavor.
One proposal for efficiently routing high-performance signals in an ATE interface is disclosed in U.S. patent application Ser. No. 09/676,041, entitled xe2x80x9cTester Interface Modulexe2x80x9d, filed Sep. 28, 2000, incorporated herein by reference and assigned to the assignee of the present invention. Generally, this proposal discloses a harness assembly for interfacing a plurality of semiconductor pin electronics circuits to a compliant interconnect array disposed on a device-interface-board. The harness assembly includes a plurality of coaxial cables having shield and center conductor distal tips that terminate in a housing. The distal tips of the cables are formed to define an interface engagement plane.
While the proposal above is beneficial for its intended purposes, the shield and center conductor contact structures are susceptible to a problem known as xe2x80x9cpistoningxe2x80x9d, due to the direct contact of the structures to the compliant array, or interposer and from bending of the cable. Pistoning involves the relative axial displacement of the center conductor with respect to the shield conductor. In some instances, if the pistoning problem is too great, the contact surfaces of the shield/signal conductors may be unable to touch the compliant interposer or distort the 50-ohm signal. Complex contact configurations could address the problem, but at an undesirable cost when considering the thousands of connections involved.
What is needed and heretofore unavailable is a tester interface module capable of delivering high fidelity signals at low cost. The tester interface module of the present invention satisfies these needs.
The interface module of the present invention provides a cost-effective and straightforward way to route dense arrays of high frequency conductors with minimal signal degradation.
To realize the foregoing advantages, the invention in one form comprises an interface module for connecting a plurality of signal paths from a first electronic assembly to a second electronic assembly. The interface module includes a plurality of coaxial cables having distal ends adapted for coupling to the first electronic assembly and proximal ends, each cable having a shield conductor and a center conductor. A stiffener formed with a plurality of throughbores receives the proximal ends of the plurality of signal cables, the stiffener having a flat termination side at one end of the plurality of throughbores. The module further includes a signal transition assembly having a flat substrate bonded to the stiffener termination side. The substrate includes respective opposite sides and is formed with spaced-apart signal paths and ground paths extending from one side to the other side. Each center conductor and shield conductor are electrically coupled to the signal paths and ground paths and mounted to the signal transition assembly to minimize relative axial displacement.
In another form, the invention comprises an ATE interface for coupling high-frequency tester channels to a device-under-test. The interface includes an interface module having a plurality of coaxial cables having distal ends adapted for coupling to the first electronic assembly and proximal ends, each cable having a shield conductor and a center conductor. A stiffener formed with a plurality of throughbores receives the proximal ends of the plurality of signal cables, the stiffener having a flat termination side at one end of the plurality of throughbores. The module further includes a signal transition assembly including a flat substrate bonded to the stiffener termination side. The substrate includes respective opposite sides and formed with spaced-apart signal paths and ground paths extending from one side to the other side. Each center conductor and shield are electrically coupled to the signal paths and ground paths and mounted to the signal transition assembly to minimize relative axial displacement. The interface further includes a device-interface-board adapted for mounting the device-under-test, and a compliant interposer disposed between the signal transition assembly and the device-interface-board.
Other features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.